feat(supplier): 供应商成本补平台内供应商供货价

- 优先 product_supplier_mapping.supply_price（统一供货价，平台内/外部）
- 无供货价则外部供应商走合同折扣 supply_contract_items
- 无映射回退 product.providerid

product_management/core.py

@@ -1442,37 +1442,60 @@ class ProductManager:
                 pass
         amount = original_amount * discount
 
-        # 3. 供应商折扣（supplychain 模块，成本侧）→ cost
-        #    供应商折扣是平台进货折扣，与客户折扣独立，不取 min。
+        # 3. 供应商成本（supplychain 模块，成本侧）→ cost
+        #    供应商成本是平台进货成本，与客户折扣独立，不取 min。
+        #    优先 product_supplier_mapping 供货价 supply_price（平台内/外部统一）；
+        #    无供货价则按外部供应商合同折扣 supply_contract_items 算。
         cost = original_amount
         try:
-            supplier_id = product.get('providerid') or ''
-            if not supplier_id:
-                # 从 supplychain 的产品→供应商映射查首选供应商
-                dbname = self._get_dbname()
-                async with DBPools().sqlorContext(dbname) as sor:
-                    maps = await sor.R('product_supplier_mapping',
-                                       {'product_id': pid})
-                    if maps:
-                        pref = [m for m in maps
-                                if str(getattr(m, 'is_preferred', '')) == '1'] or maps
-                        supplier_id = (getattr(pref[0], 'external_supplier_id', '')
-                                       or getattr(pref[0], 'supplier_org_id', '')
-                                       or '')
-            if supplier_id:
-                sc = await env.calculate_sale_amounts(None, {
-                    'resellerid': resellerid,
-                    'supplier_id': supplier_id,
-                    'productid': pid,
-                    'prodtypeid': product.get('category_id') or '',
-                    'quantity': 1,
-                    'unit_price': original_amount,
-                })
-                if sc:
-                    sc_data = json.loads(sc) if isinstance(sc, str) else sc
-                    sc_data = sc_data.get('data', {}) if isinstance(sc_data, dict) else {}
-                    supply_discount = float(sc_data.get('supply_discount', 1.0) or 1.0)
-                    cost = original_amount * supply_discount
+            dbname = self._get_dbname()
+            mapping = None
+            async with DBPools().sqlorContext(dbname) as sor:
+                maps = await sor.R('product_supplier_mapping', {'product_id': pid})
+                if maps:
+                    pref = [m for m in maps
+                            if str(getattr(m, 'is_preferred', '')) == '1'] or maps
+                    mapping = pref[0]
+
+            if mapping is not None:
+                # 首选供应商映射：优先直接供货价
+                supply_price = getattr(mapping, 'supply_price', None)
+                if supply_price not in (None, '', 0):
+                    cost = float(supply_price)
+                else:
+                    supplier_id = (getattr(mapping, 'external_supplier_id', '')
+                                   or product.get('providerid') or '')
+                    if supplier_id:
+                        sc = await env.calculate_sale_amounts(None, {
+                            'resellerid': resellerid,
+                            'supplier_id': supplier_id,
+                            'productid': pid,
+                            'prodtypeid': product.get('category_id') or '',
+                            'quantity': 1,
+                            'unit_price': original_amount,
+                        })
+                        if sc:
+                            sc_data = json.loads(sc) if isinstance(sc, str) else sc
+                            sc_data = sc_data.get('data', {}) if isinstance(sc_data, dict) else {}
+                            supply_discount = float(sc_data.get('supply_discount', 1.0) or 1.0)
+                            cost = original_amount * supply_discount
+            else:
+                # 无映射，回退 product.providerid（外部供应商走合同折扣）
+                supplier_id = product.get('providerid') or ''
+                if supplier_id:
+                    sc = await env.calculate_sale_amounts(None, {
+                        'resellerid': resellerid,
+                        'supplier_id': supplier_id,
+                        'productid': pid,
+                        'prodtypeid': product.get('category_id') or '',
+                        'quantity': 1,
+                        'unit_price': original_amount,
+                    })
+                    if sc:
+                        sc_data = json.loads(sc) if isinstance(sc, str) else sc
+                        sc_data = sc_data.get('data', {}) if isinstance(sc_data, dict) else {}
+                        supply_discount = float(sc_data.get('supply_discount', 1.0) or 1.0)
+                        cost = original_amount * supply_discount
         except Exception:
             cost = original_amount